The present invention relates to apparatus and methods for ultrasound signal processing, and more specifically, but not exclusively, relates to techniques for synthetic aperture focusing of ultrasound systems.
Existing Synthetic Aperture Focusing Techniques (SAFTs) for ultrasound systems typically sum all sampled volume elements that fall on a predicted hyperbolic surface to a single accumulator to produce a fully focused volume element, and this completed summation is recorded into a second sampled volume of focused volume elements. U.S. Pat. Nos. 6,128,092; 5,465,722; and 4,841,489 are cited as sources of further information concerning SAFT for ultrasound systems.
Generally for SAFT routines, if the sampled volume is cubic with n samples on a side, then the order of magnitude of the processing task is n5. SAFT inspections can generate data volumes with 109 total volume elements, i.e. cubes with one thousand samples on a side. If worst-case complexity is assumed, 1015 summations can result.
When the summation is restricted to a synthetic aperture the complexity of the computation can sometimes be reduced by as much as a factor of 10; however, real-time performance at this level of complexity is still often difficult to achieve with cost-effective processing equipment. Frequently, such performance is often desired for imaging and other interrogation synthetic aperture focusing applications utilizing ultrasound. Consequently, SAFT routines sometimes include skip logic to give reasonable performance by omitting the focusing of volume elements with low responses. Unfortunately, this approach may still offer unacceptable results. Accordingly, better processing techniques and/or equipment, such as transducer devices better suited to SAFT, are needed to advance SAFT-based ultrasound systems.